A rare but severe condition caused by a sudden defective production of adrenal steroids (cortisol and aldosterone). It represents an emergency and may occur at any age. Steroid withdrawal is the most common cause in patients with chronic adrenal insufficiency. A precipitating illness, surgery without adrenal support, pregnancy, any acute or chronic disease, or acute trauma are other potential causes of an acute adrenal crisis. The disorder may result from an acute exacerbation of chronic primary adrenal insufficiency. Laboratory exams show signs of adrenal insufficiency (hypoglycemia, hyponatremia and elevated natriuresis, hyperkaliemia, hemoconcentration, hypochloremic metabolic acidosis and functional renal failure) confirmed by hypocortisolemia, increased adrenocorticotropic hormone (ACTH) and an insufficient response to rapid ACTH stimulation testing.